1. Technical Field
The present invention relates to an image forming apparatus for transferring a toner image formed on the surface of an image carrier onto a recording medium at a transfer nip. The image forming apparatus may be implemented, for example, as a copier, a printer, a facsimile machine, or a multifunction peripheral having at least two of copying, printing, facsimile transmission, plotting, and scanning capabilities.
2. Description of the Related Art
An image forming apparatus forms a toner image on the surface of a drum-shaped photosensitive element functioning as an image carrier through a known electrophotographic process. An endless intermediate transfer belt that is an image carrier as an intermediate transfer body abuts against the photosensitive element, and a primary transfer nip is thus formed. The toner image formed on the photosensitive element is then primarily transferred onto the intermediate transfer belt at the primary transfer nip.
A secondary transfer roller as a transfer member abuts against the intermediate transfer belt, and a secondary transfer nip is thus formed. A secondary transfer facing roller is arranged inside of the loop of the intermediate transfer belt, and the intermediate transfer belt is nipped between the secondary transfer facing roller and the secondary transfer roller. The secondary transfer facing roller arranged inside of the loop is grounded. A secondary transfer bias (voltage) is applied from a power supply to the secondary transfer roller arranged outside of the loop. In this manner, a secondary transfer field for electrostatically transferring the toner image from the secondary transfer facing roller to the secondary transfer roller is formed between the secondary transfer facing roller and the secondary transfer roller, that is, in the secondary transfer nip.
The toner image on the intermediate transfer belt is then secondarily transferred onto a recording sheet fed into the secondary transfer nip at operational timing synchronized with the toner image on the intermediate transfer belt, by the effects of the secondary transfer field and a nipping pressure.
In such a structure, when a recording sheet with a highly textured surface such as washi (Japanese paper) is used, density patterns following the texture of the surface could be more easily formed in an image. These density patterns are caused because a sufficient amount of toner is not transferred onto recessed parts of the paper surface, and the image density in the recessed parts becomes thin compared with that in projected parts.
An object of the present invention is to provide an image forming apparatus for suppressing formations of white spots and achieving high quality images, while obtaining sufficient image densities in both of the recessed parts and the projected parts of a recording medium surface.